Create ARCHITECTURE.md (#856)

* Create ARCHITECTURE.md

* Update ARCHITECTURE.md

doc/ARCHITECTURE.md

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+## minecraft-data architecture
+Key Details:
+* Langauge independent repository holding data for many Minecraft versions, including Java Edition versions after 1.7 and Bedrock Edition versions after 1.16
+* Has data on blocks, items, network protocol packet structures, entities and more
+* The data in this repo is generated using several tools as described in the `doc/add-data-new-version.md` file for Java Edition and `doc/bedrock.md` for Bedrock Edition
+
+File Structure:
+* Most data is stored in JSON. The JSON schemas for these files are stored inside the `schemas/` folder.
+* `data/pc` contains data for minecraft java edition separated by folder and `data/bedrock` for bedrock edition
+* `data/dataPaths.json` has a mapping for minecraft version to data type to folder to find that data.
+  * It looks like `{"pc": { "1.16": {"blocks":"pc/1.16"} } }`, meaning java edition block data for version 1.16 can be found in `pc/1.16` under the name `blocks.json`. If the data didn't change from 1.15, it might point to `pc/1.15` instead.
+* `tools/js` contains Node.js scripts to do maintenance on the repository, such as running tests to ensure data validity and also contains some files used to generate data inside the repository.
+
+Usage:
+* As documented in the README.md, there exist several wrappers that expose the data inside minecraft-data. Notably, this includes PrismarineJS/node-minecraft-data, which exposes the data as a NPM package. 
+
+Contributing Tips:
+* Files should generally be obtained with the use of a data extractor or generator, as mentioned above
+* If you make a PR with new data, describe how you obtained the data, as otherwise we won't be able to obtain that data for future versions
+* Checkout the `.github/workflows` directory to see how tests are run on the repo